1. Field of the Invention
The present invention is related to ensure and facilitate history management of a wheel supporting bearing unit which rotatably supports a wheel to a suspension system of a vehicle.
2. Description of the Background Art
A wheel 1 which makes up a road wheel of a motor vehicle and a disk brake which constitutes a braking system of the motor vehicle are rotatably supported on a knuckle 3 which makes up a suspension system of the motor vehicle by way of a construction shown in FIG. 19 (refer to, for example, Japanese Patent Unexamined Publication No. JP-A-2005-014906). Namely, an outer ring 6 or a stationary ring which makes up a wheel supporting bearing unit 5, which is a target of the invention, is fixed to a circular supporting hole portion 4 formed in the knuckle 3 by fastening a fastening flange 7 which is formed on an outer peripheral surface of the outer ring 6 to the knuckle 3 with not-shown several bolts. A hub 10 which is a rotational member made up of a hub main body 8 and an inner ring 9 is rotatably supported on an inside diameter side of the outer ring 6. This inner ring 9 is fitted on a small-diameter step portion 11 which is formed at a portion of an axially intermediate portion of the hub main body 8 which lies closer to an inner end portion thereof (here, “axially inboard” denotes a portion lying at a center of the vehicle in a width direction when the hub is assembled on to a vehicle, or lying to a right-hand side in each drawing. On the contrary, a left-hand side in each drawing which lies outside of the vehicle in the width direction when the hub is assembled on to the vehicle is denoted by “outer side”. This is also true in the specification and the claims of the invention). In addition, an axially inboard end face of the inner ring 9 is held by a clamping portion 12 formed at an axially inner end portion of the hub main body 8, so as to fix the inner ring 9 to the hub main body 8.
In order to rotatably support the hub 10 configured as has been described above on the inside diameter side of the outer ring 6, a plurality of rows of outer ring raceways 13a, 13b are formed on an inner peripheral surface of this outer ring 6. In addition, a plurality of rolling elements 15, 15 are rotatably provided between these two outer ring raceways 13a, 13b and a plurality of rows of inner race raceways 14a, 14b which are formed on, respectively, an outer peripheral surface of the axially intermediate portion of the hub main body 8 and an outer peripheral surface of the inner ring 9, respectively, so that the plurality of rolling elements 15, 15 are allowed to rotate in each of the rows while being retained by each of cages 16, 16. Note that taper rollers may be used as the rolling elements for a wheel supporting bearing unit for a heavy vehicle.
In addition, a mounting flange 17 is formed at a portion of an axially outer end portion of the hub main body 8 which projects from an axially outer end portion opening of the outer ring 6. The wheel 1 and the rotor 2 are fitted on a cylindrical portion 18 provided on the axially outer end portion of the hub main body 8 by loose fit and are fixedly held to an axially outer surface of the mounting flange 17 with a plurality of studs 19 and nuts, not shown.
Additionally, an encoder 20 is fitted on an axially inner end portion of the inner ring 9. Then, the rotational speed of the encoder 20 is made to be detected by a rotational speed detection sensor 22 which is supported on a cover 21 fixed to an axially inner end portion of the outer ring 6. The rotational speed of the hub 10 constituting the rotational ring that is detected by the rotational speed detection sensor 22 is used to control a running state stabilizing system such as an anti-locking brake system (ABS) and a traction control system (TCS).
Note that since the illustrated example is the wheel supporting bearing unit 5 for driven wheels (front wheels of an FR vehicle or RR vehicle, rear wheels of an FF vehicle), the hub main body 8, which makes up the hub 10, is made to be a solid element (substantially cylinder solid). In contrast to this, although not illustrated, as described in the JP-A-2005-014906, in the case of a wheel supporting bearing unit for driving wheels (rear wheels of an FR vehicle or RR vehicle, front wheels of an FF vehicle, all wheels of a 4WD vehicle), a splined hole is formed in a radially central portion of a hub main body, so that a splined shaft of a constant velocity joint is inserted into the splined hole. In addition, an outer ring rotating type wheel supporting bearing unit has conventionally been known in which an inner race does not rotate and an outer ring does rotate.
Incidentally, in recent years, the importance of securing traceability for (ability to find the origin of) products is increasing in various fields for the purposes of securing the safety (reliability) of products, as well as implementing quick countermeasures against drawbacks of products which have already been distributed to the market. To be specific, it is required to secure a means for tracing (or dealing with retrospectively) to obtain (inquire) historical information of history control such as information of production, distribution, maintenance and service, and disposal of the products.
On the other hand, the traceability is conventionally attempted to be secured by stamping the information of production date, production lot and the like on wheel supporting bearing units. To describe specifically, in the event that a defect such as a failure is found in a wheel supporting bearing unit, historical information is obtained (inquired about) on production history for the wheel supporting bearing unit, which is found defective, from information of the production lot or the like which is (part of the historical information) stamped thereon. Then, by utilizing the historical information so obtained, models of the vehicle are specified on which wheel supporting bearing units which are likely to be subjected to the same failure are installed, and a cause of the defect can be investigated, and furthermore, a rectifying treatment can be implemented.
In the case of the method of stamping the required information as described above, however, there is a possibility that the following problems could be caused from the viewpoint of ensuring the traceability of wheel supporting bearing units.
Namely, when stamping information of a wheel supporting bearing unit, stamping needs to be implemented at a location selected as being difficult to be subjected to damage or wear even in use over a long period of time, and hence, since there is imposed a limitation on space where stamping can be implemented, it becomes difficult to stamp much information. In addition, stamping much information within a limited space is troublesome work and requires much time and many manhours, and there is caused a problem with securing the visibility of information so stamped. Due to this, in many cases, information that is to be stamped on wheel supporting bearing units are limited to part of the historical information such as information of production date, production lot and the like. As a result, in order to inquire (find) into detailed historical information such as one on production or assembly plants, repair history or the like based on the limited small amount of information by utilizing, for example, a database inputted in advance into a terminal, not only much time and many manhours are required but also there exists a possibility that no accurate historical information is obtained.
Furthermore, the information of production lot or the like that is stamped on a wheel supporting bearing unit cannot be read directly from the outside of a motor vehicle once the wheel supporting bearing unit is assembled to the vehicle. Due to this, although there occurs an urgent need to verify the information of production lot or the like, the relevant motor vehicle needs to be sent to a repair shop where the wheel supporting bearing unit in question is removed for verification. In addition, in a case where stamping is implemented in an interior of a wheel supporting bearing unit, since disassembling work is required for this wheel supporting bearing unit, much time and many manhours are also required.